Process for preparing metal carbonyls



United States Patent PROCESS FOR PREPARING METAL CARBONYLS Rex D.Closson, Northville, and George G. Ecke, Ferndale, Mich., and Lloyd R.Buzhee, Huntington, W. Va., assignors to Ethyl Corporation, New York,N.Y., a corporation of Delaware No Drawing. Application October 3, 1956Serial No. 613,595

11 Claims. (Cl. 23-203) This invention relates to transition metalcarbonyls and to a novel method for the preparation of these compounds,particularly chromium and manganese carbonyls.

The transition metal carbonyls are useful compounds both as chemicalintermediates and in certain direct commercial uses. In the past greatdifficulty has been experienced in preparing certain of these transitionmetal carbonyls in high enoughyield to make their use commerciallyfeasible. In particular no process has been known heretofore whichproduces manganese carbonyl in sufficient yield to make its industrialapplication an achieved practicality, even though this compound is knownto have valuable utility both as an antiknock agent in liquidhydrocarbonfuels, and as an intermediate for preparing other manganese compounds.

It is, therefore, an object of this invention to provide a novel processfor the synthesis and manufacture of transition metal carbonyls. Anotherobject is to provide a process for the manufacture of chromium carbonyl.A particular object of this invention is to provide a process for theproduction of manganese carbonyl in good yield.

The above and other objects of this invention are accomplished by aprocess for preparing transition metal carbonyls which comprisesreacting carbon monoxide with acompound having the formula.

where A is an element of group V of the periodic table having an atomicnumber no greater than 15, i.e., nitrogen and phosphorus, R and R areorganic'groups characterized by the absence of (1) olefinic unsaturationand (2) a hydrogen atom on the carbon atom immediately adjacent thecarbon atom to which the group V element is bonded, R is an organicradical, M is a transition metal, 2: and y depend upon the valence of M,x ranging from 1 to 3 inclusive, and y ranging from 1 to 2 inclusive. Bytransition metal is meant a metal of groups IVB, VB, VIB, VIIB and VIIIof the periodic table.

The compound elucidated in the above general formula is referred toherein as the transition metal intermediate" and is formed, for example,as the reaction product of a transition metal salt and a non-transitionmetal intermediate. This latter intermediate is conveniently prepared byreacting a metal with an organic compound having the formula:

wherein'R R 'R, and A are asdefined above. The

intermediates in this reaction haveformulaecorresponding to:

wherein 'M', M" and'M' represent mono-, di-, and'trivalent metalsrespectively, A, R R and R are as defined above. The non-transitionmetals preferred in the preparation of these intermediates include thealkali metals, alkaline earth metals, and aluminum.

The radical R in the above'formulae is an organic radical inclusive ofalkyl, aryl, .alkenyl, alkaryl, aralkyl radicals and the like. Theseradicals contain'from 1 to about 16 carbon atoms. Organichydrocarbon'radi' cals are preferred.

A preferred class of compoundsfor use in the preparation of themetal-containing intermediates referred to above are those 'in'which .A.in the :aboveformulaeis nitrogen; that is, an imine compound. Compoundsof this type are preferredasxthey are more readily prepared than thecorresponding phosphorus compound, andtheir use leads to excellentyields of metal carbonyls. N- benzohydrylidenephenylimine which. hasthe'formula:

intermediate is formed as the reaction product of a transition metalsalt and monosodio benzohydrylidenephenylimine. This embodiment of theinvention is particularly applicable of the synthesis ofmanganesefcarbonyl.

The non-transition metal intermediate is prepared from the metal and animine meeting the above requirements, by adding the metal to anequivalent amount of the imi-ne compound. Alternatively, the reverseprocedure may be employed when convenient. When the metal isparticularly reactive the process ispreferably carried out in an inertatmosphere under conditionssuch that neither the metal nor the productintermediate come in contact with the air. Thus, for example, adispersion of sodium in mineral oil is added tobenzohydrylidenephenylimine while the system is agitated and kept undera nitrogen atmosphere. It is often advisable toheat the mixture atreflux to prepare'the non-transition metal intermediate.

The transitionrnetal intermediate is conveniently prepared from thenon-transition metal intermediate by metal interchange. That is, a-saltof the transition metal is reacted with the non-transition metalintermediate. Elevated temperatures are employed when necessary tocomplete the reaction. y

The transition metal intermediate is also prepared by reacting anappropriate imine with a non-transition metal in the presence of atransition metal salt. In this manner the transition metal intermediateis prepared from the non-transition metal intermediate as the latter isformed.

The process of this invention is conveniently carried out in an inertsolvent. A preferred class of solvents comprise cyclic ethers such asdioxane and tetrahydrofuran.

The transition metal intermediate is reacted with carbon monoxide in theprocess of this invention to form the transition metal carbonyl. Thiscarbonylation is carried out in a sealed vessel at elevated temperaturesand pressures. A preferred method of carrying out the reaction withcarbon monoxide comprises pressurizing the vessel with carbon monoxidewhile the contents of the vessel, that is, the reaction mixture from thepreparation of the transition metal intermediate is at room temperature.After the vessel has been pressurized with carbon monoxide and sealed itis then heated slowly to the reaction temperature and allowed to remainat that temperature until the reaction is substantially complete.Reaction temperatures of from about 50 C. to about 500 C. and pressuresfrom about 200 to about 10,000 p.s.i.g. are employed. Reaction time offrom about /2 hour to about hours is ordinarily sufiicient.

Embodiments of the instant invention will become apparent by referenceto the following specific examples in which all parts and percentagesare by weight.

Example I .To a glass reaction vessel equipped with gas and liquid inletmeans, heating means and reflux condenser was charged 800 parts oftetrahydrofuran and 129 parts of- N-benzohydrylidenephenyliminc. Thecontents of the vessel were kept under an atmosphere of nitrogen and thetemperature was controlled at C. while 23 parts of a 50 percent sodiumdispersion in mineral oil were added. After the sodium addition vwascompleted, 31.5 parts of manganous chloride were added while the mixturewas agitated. The resultant intermediate was charged to a pressureresistant vessel having a plurality of gas inlet and outlet means,pressureand temperature measuring devices, heating and cooling means,and an arrangement for charging and discharging liquids and solids. Thevessel was flushed with nitrogen and pres surized with carbon monoxideat room temperature and heated gradually over a 50-minute period to amaximum temperature of 150 C. and a, maximum pressure of 3000 p.s.i.g.These conditions were maintained for an additional 40'minutes, afterwhich time the vessel was cooled, vented and the contents discharged.The reaction mixture was hydrolyzed with 200 parts of water and steamdistilled. The portion distilling above 80 C. was extracted withbenzene; the benzene extract was concentrated by distillation and 5.8parts of dimanganese decacarbonyl, [Mn(CO) melting at 149-152 C. wererecovered. This material is a yellow orange crystalline solid melting at156 C; when pure. Flame photometric analysis of the benzene extractbefore concentration indicated that the reaction produced a total ofover 12 parts of dimanganese dicarbonyl representing approximately a 25percent yield. a

v Example II I The general procedureot. Example- I was followed with thefollowing differences: The reaction intermediate which.

from 90 parts of benzohydrylidene-n-hexylimine, 630 parts oftetrahydrofuran. as. a solvent,. 15.6 parts of sodium .,dispersion,. and2 1.4 ,p a 1 "ts of manganous chloride. The pressure resistant vesselwas heated under Carbon ..70 was chargedto the pressure resistant'vesselwas prepared .4 monoxide pressure over a one hour period to 200 C. and3000 p.s.i.g. These conditions were maintained for 30 minutes. Thereaction gave an 11 percent yield of dimanganese decacarbonyl asmeasured by the flame photometer.

Example III Example IV To a glass reaction vessel of the type describedin Example I is added 350 parts of n-decyl-p,p'-dirnethylbenzohydrylidenimine (p-CH C H C=NC H 450 parts of dioxane and 107 partsof manganous bromide. To this mixture is added 40 parts of potassium inincremental portions. The temperature of the vessel is maintainedbetween 20 and 30 C. during the potassium addition. When the addition iscompleted, the mixture is refluxed for about half an hour, cooled andcharged to a pressure resistant vessel of the type described in ExampleI. The vessel is sealed, charged with carbon monoxide, and heated overapproximately a one and a half hour period to 300 C. and a maximumpressure of 10,000 p.s.i.g. These conditions are maintained. for anadditional 30 minutes, after which time the vessel is cooled, vented andthe contents are discharged, hydrolyzed and rectified as described aboveto produce a good yield of dimanganese decacarbonyl.

The reaction mixture obtained on an addition of the metal to a mixtureof imine compound and the transition metal salt in an appropriatesolvent is less viscous than the product obtained when the transitionmetal salt is added to the reaction product of the metal andthe organiccompound. Thus, the procedure used in Example IV greatly facilitateshandling of the intermediates from the glass reaction vessel to thepressure vessel .used in the carbonylation step of the reaction.Substantially identical yields are obtained under identical conditionsof temperature, pressure and time of reaction regardless of the mannerof preparation of the transition metal intermediate. The procedure asoutlined in Example IV is preferred as the final reaction mixture ismore easily handled and is prepared with one less reaction step than isnecessary when the metal is reacted initially with the imine in theabsence of the transition metal salt.

As a variant in the above procedure, the metal may be 7 added to themixture of the organic compound, the transition metal salt and thesolvent while the mixture 1 is maintained at reflux temperature. Thislatter method is advantageous in that a portion of the heat liberated bythe metal addition is utilized in the process.

Example V The procedure of Example IV is repeated using 9 parts ofaluminum, 63 parts of manganous chloride, 600 a parts of the dimethylether of ethylene glycol as a solvent and 322 parts ofp,p'-dichlorobenzohydrylidene benj; The carbonylation reaction iscarried out at 200 C. and 50,000 p.s.i.g. for 15 minutes after apreliminary heating period of one hour. A good yield of dimanganesedecacarbony results.

I the preliminary heating is conducted in the absence of carbonmonoxide, and when the reaction mixture reaches 200 'C., the vesselispressurized with carbon monoxidm to 50,000 p.s.i.g. and the mixturereacted for'15 minutes.

A greatly reduced yield off dimanganese decacarbonyl results-1 Example.VII.

Therrprocedurejwofi Example IV is repeated tusinge 8005- partsiofw-tetrahydrofuran, 5 3 parts of: chromic chloride, 44-Ipartsofrstrontiumrmetal and-;290 parts of "3,3,5;5a

tetramethylw 4 I- heptylidene rn ethylphenyl phosphine; [CH CI-I C.( CHG=P;-.(m'C H C H .1: The 1. carebonylatiomreactionis' carried out at3000p.s.i.g. and 200i? C. .for'-30 minutes;rafter acne hour periodtobringthe reaction mixture to these conditions.chromium.hexacarbonyl-results.

Example VIII The procedure of Example VII is followed using 500 parts ofdioxane, 66 parts ofchromic sulfate, 6 parts of magnesium metal and130'parts of benzohydrylidenephenylimine. An excellent yield of chromiumhexacarbonyl results.

Example'JX A good yield of dimanganese decacarbonyl is producedfollowing the general procedure of Example VII using 600 parts ofdioxane, 87 parts'of manganous acetate, 23 parts of sodium and 232 partsof (C H C=PCH benzohydrylidenemethylphosphine.

Example X Example VII is repeated using 900 parts of toluene, 113partsof chromic-iodide, 23 parts ofsodiumyand355 partsofp,p'-dinitrobenzohydrylidene n-hexylimine:

which:,contains no hydrogen on acarbon atom adjacent; These compoundshave-at least. 1O.1, carbon atoms, and. those having up to 25 carbonvatomsu the.v imino. carbon.

in the molecule are suitable in the practice of this .invention...Examplesof such compounds, are, p,p-diamino benzohydrylidenemethylimine, p,p -diphenylb.en z ohy drylidene --n, hexyl .phosphine,m,m' dinitrobenzohy drylidene benzyl phosphine,4,4,6,6-tetra1r1ethyl-5-nonyl-- ideneethylimine, and the like.

Howevena; preferred class of compoundscomprise" the imines which have nohydrogen alpha to theimino carbon and which contain-from 10 to about2.0. -carb'on- These compounds are preferred -as it has;.bee11-l atoms.found that a good yield of metal carbonyl is produced when they areemployed. Examples of these include benzohydrylidenephenylimine,a2,2,4,4,-tetramethyl 3 pentylidene methylimine, p-methylbenzohydrylidenebenzylimine, benzohydrylidene-n-hexylimine, 2,4-diethyl-2,4dimethyl-3-pentylidene p nitrophenylimine and; the it like Thenon-transition metal which is reacted with the;

iminein preparing the intermediate is a reactive-.metal selected fromthe group consisting of alkali metals,,,al-; kaline earth metals,aluminum and the like. Thus, sodi um, lithium, potassium, rubidium,cesium, beryllium,

magnesium, calcium, strontium, barium and'alurninnrrr are allusefuI-inpreparingthe non-transition metal inter: mediate intheupractice of this invention, The;alkalirnet als are preferred as itis found that high yields of carbon- A yl are obtainedi by their-use,Ofthe alkali metals; so.

dium is particularly preferred-as. itis readilyavailablm; andgreacts;rapidly. with the;..ketone ,to. give; azhighnyieldi of the'intermediate.

When the metal :used; is .OIlBsWhlCh is sensitive:.1tox-air1 or water,it is preferably used in the form .ofaidispersionin a. suitable i inertcarrier." such as: anhydrous mineral A ,good yield Set:

A.-. lower yield of chromium carbonyl results than that'- oil. It isoften advisable to add the metal in amalgamated, fom-to-insurereaction:

The transition metal compounds which are I used "inthe process of thisinvention to produce the transition metal intermediate include generallythe ionic compounds of the metal such as the halides including thebromides, iodidtes and'chldrides; the nitrates, sulfates, oxalates,acetates and' otlier ionic organic and inorganic-salts. Ex-- amples 1 of-a these: are MnCl MnBr Mnl MnSO;, manganous-oxalate, manganous acetate,CrClg, Cr'Br CrI chromic'acetate, chromic sulfate, and the like.

The process ofthis invention is most advantageously carried' out in' -asuitable solvent. In general,]organic*- solvents awh'ich areinert to thereactants under' the conditionsrof thetreaction are suitable. Examplesof "suitable solvents include benzene, toluene, hexane andlike-hydrocarbonsL. Particularly good results are obtained when thesolvent employed is an inert, polar, non-reactive cyclic: ether, suchasdioxane; ticularlyipreferred solvent of this latter type.-

Whenthe transition metal intermediate is reacted with" carbommonoxide atelevated temperature and-pressurehigher yields of carbonyl are obtainedwhen theintermediateiis contacted with :carbon monoxide at temperaturesand pressures substantially below final reaction conditions.-. If;after=this initial contact the reaction massis thengheatedztothe-properconditions of temperature and pressure; a.- .good yield :of carbonylresults. The process of thiszinvention is also operative whenthetransition metal intermediate.iszheated in the absence of carbonmonoxide;and-: then contacted with carbon monoxide atelevatediitemperatures. However, the yield of carbonyl producedbyathis'aprocedure. is substantially lower as illustratedbyE-xample .VI.

The 'zcarbonylation step is conveniently carried out=at onimonoxidepressures of from about 250 p.s.i.g. to

pressuressabovei 50,000 p.s.i.g. Pressures of 'from 500'- p.s. i.g-t.to10,000 .p.-s.i.g.:are preferred as agood yield 015 metal Icarb'onylcan=bev -separated from the reaction miX-- ture -when pressures-inthisrangeare employed: Pressures of;-from.500:=to3,000 p.s.i.g. areparticularlypreferredas they-canybe.safely obtained in readily availableprocessingequipment.

Within; the pressure range, outlined above the carbonylationa stepisconveniently carried'out at temperatures between 5-0 and 300C.Temperatures of from to 230, C. are preferred as an excellent yield ofcarbonyl is produced. at these temperatures.

After the. reaction mixture in contact with carbon monoxidereachesreaction conditions the temperatureand' carbon monoxide pressure areconveniently maintaineduntil thei; reaction has produced a high yield ofmetal carbonyl. If desired, reaction conditions can-be maintained,until, ,the;system no longer absorbs carbon 111.0111 M oxide. However,reaction times of as little as l5- minutes canbeemployed to giveasatisfactory yield of carbonyl. Generally; reactiontimes of between 0.5hour and 2.5 hours. are:preferred as excellentyields of carbQnyl aF-eobtained in: this manner;

Theyamount of solvent employed in the process of this inventlondsdependent upon the fluidity required of the reaction mass prior to thecarbonylation step and the method of preparation of the transition metalintermedi ate; When theintermediate is preparedas described-in-ExampleJV av lower proportionof solvent can be-employed due to theincreased fluidity of the reaction mass: However, when the procedureused in Example I is followed a more viscous intermediate results andthus a higher concentration of solvent is necessary particularly whenthe intermediate is prepared in-a vessel other than that in which thecarbonylation is. conducted. In gen eral, an amount of solventequivalent to a weight ratio of from 4:1 to 30:1 of solvent to organicimine employed is used. The preferred range comprises a solvent to,imine weight;ratio';,ofjfrom 5:1 to 10:1 aslow viscosity inter:

Tetrahydrofuran is a-par-*" proportion of metal carbonyl For example,dimanganese decacarbonyl is extracted from the steam distillate by theuse of such inert organic solvents as cyclohexane, benzene, toluene andthe like.

As pointed out above the transition metal carbonyls prepared by theprocess of this invention find utility as fuel additives, and inparticular manganese carbonyl is an antiknock agent of outstandingefiect in gasoline and other liquid hydrocarbon fuels.

The term gasoline pertains to liquid hydrocarbons and is inclusive ofmixtures of aliphatic, olefinic, aromatic and naphthenic hydrocarbonsderived from mineral sources such as petroleum, coal, shale and tarsands, and which includes straight run, reformed, cracked and alkylatedstocks, and mixtures of these. The initial boiling point can be fromabout 70 to about 90 F. and the final boiling points vary from less than300 to more than 440 F.

To a gasoline meeting the above requirements was added variousquantities of dimanganese decacarbonyl and the mixtures were agitated togive a homogeneous fuel blend. Tests were conducted of these fuel blendsusing a single cylinder CFR standard test engine according to theAmerican Society for Testing Materials; procedure D9D8-51 to determinethe octane number of the fuel containing the dimanganese decacarbonyland the identical fuel with no antiknock additive. This procedure isreferred to as the Research Method for Antiknock Testing. The additionof dimanganese decacarbonyl in quantities sufiicient to give 0.5, 1.0,and 1.5 grams of manganese per gallon of fuel, resulted in fuels havingoctane ratings of 84.9, 88.1, and 90.8 respectively. The fuel whichcontained no dimanganese decacarbonyl gave an octane number rating of77.1. 3.75 gramsvof lead as tetraethyllead are required to produce anoctane number increase in this fuel equal to that produced by theaddition of 1.5 grams of manganese as dimanganese decacarbonyl. Thedirnanganese decacarbonyl is, therefore, 2.5 times as effective astetraethyllead.

When employed as an antiknock agent, the dimanganese decacarbonylprepared by the process of this invention is conveniently used inconjunction with other fuel additives. Thus, other antiknock agentsscavengers, dyes and antioxidants are advantageously added to the fuelalong with metal carbonyl. Similarly, antiknock fluid compositionscontaining any or all of the above ingredients in addition to the metalcarbonyl find utility as fuel additives.

The various other metal carbonyls such as chromium, iron carbonyl,nickel carbonyl, cobalt, and the like, find various uses which are wellknown in the art. For example, chromium carbonyl and iron carbonyl findutility in the gas phase plating of other metals. Further, thesecompounds are a convenient source of the pure metal by the decompositionof the carbonyl.

We claim:

1. A process for preparing a transition metal carbonyl which comprisesreacting carbon monoxide with a compound having the formula:

R1 Rs r-C- 1 3.1- -A i I 3 I where A is an element of group V of theperiodic table having an atomic number no greater than 15, R and R,

are organic hydrocarbon absence of (1) olefinic uusaturation and (2.) ahydrogen atom on the carbon atom immediately adjacent the carbon atom towhich the group V element is bonded,

R is an organic hydrocarbon radical, M is a transition metal selectedfrom the class consisting of the metals of groups IVB, VB, VIB, VIIB andVIII of the periodic table, 1: and y depend upon the valance of M, xranging from 1 to 3 inclusive and y ranging from 1 to 2 inclusive.

2. The process of claim 1 wherein said group V element is nitrogen.

3. The process for the preparation of dimanganese decacarbonyl whichcomprises reacting carbon monoxide with the compound represented by theformula:

4. A process for preparing a group VIIB metal car bonyl which comprisesreacting carbon monoxide with a compound having the formula where R andR, are organic hydrocarbon groups characterized by the absence of (1)olefinic unsaturation and (2) a hydrogen atom on the carbon atomimmediately adjacent the carbon atom bonded to nitrogen, R is an organichydrocarbon radical, and M VIIB transition metal.

5. The process of claim 4 where the group VIIB transition metal ismanganese.

6. A process for the preparation of a transition metal carbonyl whichcomprises the steps of (A) reacting a nontransition metal selected fromthe class consisting of alkali metals, alkaline earth metals andaluminum with a compound having the formula where R and R, are organichydrocarbon groups characterized by the absence of (1) olefinicunsaturation and (2) a hydrogen atom on the carbon atom immediatelyadjacent the carbon atom bonded to nitrogen and R is an organichydrocarbon radical; (B) reacting the product from step (A) with atransition metal salt selected from the class consisting of salts of themetals of groups IVB, VB, VlB, VIIB and VIII of the periodic table and(C) reacting carbon monoxide with the product of step 7. The process ofclaim 6 where the transition metal salt is a group VIIB metal salt.

8. The process of claim 7 where the group VIIB metal salt is a manganoussalt.

9. Process of claim 8 where the 10. Process for the preparation ofdimanganese decacarbonyl which comprises the steps of (A) reacu'ngsodigroups characterised the is a group um withN-benzohydrylidenephenylimine; (B) reacting the product of (A) Withmanganous chloride; and (C) reacting the product of (B) with carbonmonoxide at 150 C. and a maximum carbon monoxide pressure of 3000p.s.i.g.

11. The process of claim 1 wherein the reaction is conducted attemperatures of from 50 to about 500 C.

and carbon monoxide pressures of from a'iiout 200 to" about 10,000p.s.i.g.

References Cited in the file of this patent Deming: General Chemistry,5th edition, John Wiley

1. A PROCESS FOR PREPARING A TRANSITION METAL CARBONYL WHICH COMPRISESREACTING CARBON MONOXIDE WITH A COMPOUND HAVING THE FORMULA: